In general, a display device refers to monitors for a TV or a computer as a whole, and comprises a display device forming an image and a case supporting the display device.
Examples of the display device may comprise a plasma display panel (PDP), a liquid crystal display (LCD), an electrophoretic display, and a cathode-ray tube (CRT). An RGB pixel pattern for implementing an image and an additional optical filter may be provided in the display device.
The optical filter may comprise at least one of a reflection prevention film preventing the light that is incident from the outside from being reflected to the outside, a near IR shield film shielding the near IR generated in the display device in order to prevent mis-operation of electronic devices such as remote controllers, a color correction film increasing the color purity by controlling a color tone by comprising a color control dye, and an electromagnetic wave shield film shielding the electromagnetic wave generated in a display device when a display apparatus is driven. Here, the electromagnetic wave shield film comprises a transparent substrate and a metal mesh pattern provided on the substrate.
Meanwhile, with regard to the display apparatus, as the spread of IPTVs is accelerated, a demand for a touch function that uses hands as a direct input apparatus without a separate input apparatus such as remote controllers is growing. In addition, a multi-touch function for recognizing a specific point and taking notes is required.
The touch panel performing the aforementioned function may be classified into the following types according to the detection manner of a signal.
That is, examples thereof comprise a resistive type detecting a position pressed by pressure in a state where a direct voltage is applied while changing a current or voltage value, a capacitive type using capacitance coupling in a state where an alternating voltage is applied, an electromagnetic type detecting a selected position in a state where a magnetic field is applied as a change in voltage, and the like.
Among them, the resistive type and capacitive type touch panels that are most extensively spread recognize the touch by a change in electric contact or capacitance by using the transparent conductive film such as the ITO film. However, since the transparent conductive layer has high resistance of 100 ohms/square or more, the sensitivity is lowered when the display device is manufactured in a large scale, and as the size of screen is increased, the cost of the ITO film is rapidly increased, accordingly, it is not easy to perform commercialization thereof. In order to overcome this, there is an effort to implement enlargement by using a metal pattern having high conductivity.
As described above, in the case where the display apparatus comprises the electromagnetic wave shield film or touch panel comprising a metal pattern, there is a problem in that the electromagnetic wave shield film and the touch panel cause interference with a pixel pattern and an electrode pattern of the display or a pattern structure of another optical film, thus causing a moiré phenomenon. Herein, the moiré means an interference pattern formed when two or more regular patterns overlap.
As an example thereof, since the pixel pattern of the plasma display panel (PDP) and the metal mesh pattern for electromagnetic wave shielding of the optical filter coexist in the plasma display panel (PDP), a moiré phenomenon may occur. Therefore, in general, if the specification of the plasma display panel (PDP) is determined, an effort for solving the moiré phenomenon is performed through a design of the metal mesh pattern of the optical filter.
As described above, the line width, the pitch, and the angle of the metal mesh pattern for the electromagnetic wave shielding are controlled in order to remove the moiré, but there is a problem in that it is necessary to correspond to different patterns according to the size of the display and the pixel implementation method.
In particular, the recently developed plasma display panel comprises a more precise pixel pattern in order to implement a high resolution, thus increasing the possibility of the moiré. Accordingly, there is a limit in improving the moiré by only controlling the line width, the pitch, and the angle of the known pattern.